1. Field of the Invention
The present invention relates to methods of producing fluids through a well bore from a fluid producing formation, wherein an inside diameter surface of a down-hole tubular is subjected to a smoothing process prior to being located within the well bore. The invention also relates to a smoothing process for the inside diameter surface of drill pipe used to circulate drilling fluids during well completion, both smoothing processes involving an electropolishing treatment as one step in the smoothing process.
2. Description of Related Art
The oil and gas industry is constantly seeking new ways to efficiently and economically increase production of hydrocarbon fluids. There are various ways to approach this challenge, many of which involve improvements to the oil country tubular goods, or down-hole tubulars, through which the fluids flow to the surface. There are many different factors that affect the performance of down-hole tubulars and reduce fluid flow rates including: pipe corrosion, clogging, and fluid flow friction. Corrosion occurs when a corrosive agent attacks and deteriorates the inside diameter surface of the down-hole tubular, resulting in a shortened operational life and high maintenance costs. Clogging is the accumulation of sludge and debris, such as paraffin and scale, on the inside diameter surface. Clogging results in restricted flow and reduced production. Fluid flow friction in down-hole tubulars creates significant pressure losses, resulting in reduced flow rates and decreased fluid production. If these three flow-rate reducing factors could be reduced or eliminated, fluid production could be increased, maintenance time and costs could be reduced, operational life could be extended, and smaller diameter production tubing could be used to produce the same amount of fluids that are currently being produced through larger diameter production tubing.
The present invention is concerned, in one aspect, with a smoothing process for down-hole tubulars, both those tubulars formed from corrosion resistant alloy materials (CRA) and those tubulars formed from carbon steel alloys (carbon tubing), which smoothing process involves electropolishing as an integral step.
In another aspect of the present invention, carbon steel drill pipe is subjected to a smoothing process which again involves electropolishing as an integral step in the inventive method. Drill pipe benefits from the electropolishing process in terms of both added corrosion resistance and increased flow in the same manner as do the down-hole tubular goods.
There is a need for a method of producing fluids from a fluid producing formation through down-hole tubulars in a well bore, wherein corrosion, clogging, and fluid flow friction are reduced, thereby increasing fluid production.
It is therefore an object of the present invention to provide a method of producing fluids from a formation which includes the step of subjecting the inside diameter surfaces of the down-hole tubulars to an electropolishing treatment prior to assembly and installation into the well bore. The electropolishing treatment serves to smooth the inside diameter surface, thereby reducing corrosion, clogging, and fluid flow friction. The method includes the general steps of providing a plurality of down-hole tubulars each having an inside diameter surface; subjecting each inside diameter surface to a cleansing treatment to remove thread compound from the tubular ends and to remove contaminants from each inside diameter surface; subjecting each inside diameter surface to a pickling treatment to remove mill scale; subjecting each inside diameter surface to a mechanical polishing treatment to produce a smooth surface having an arithmetic average roughness value (Ra) of less than 100 microinches; subjecting each inside diameter surface to an electropolishing treatment to produce a smooth surface having an arithmetic roughness value of less than 50 micro inches; subjecting each inside diameter surface to a post-electropolishing treatment to remove byproducts of the electropolishing treatment and assist drying; connecting the plurality of down-hole tubulars together to form a production pipe; locating the production pipe within the well bore adjacent the fluid-producing formation; and producing the fluids to the earth""s surface through the inside diameter of the down-hole tubulars.
It is another object of the present invention to provide a down-hole tubular made of a high chromium content, corrosion resistant alloy, which has been subjected to an electropolishing process to provide an inside diameter surface having an arithmetic roughness value of less than 50 micro inches, preferably less than about 30 micro inches and most preferably below about 20 micro inches.
It is also an object of the present invention is to subject traditional carbon steel tubulars and drill pipe, including upset pipe, non-upset pipe, and pipe having both threaded and plain ends to an electropolishing treatment to produce a smooth surface having an arithmetic roughness value of less than 100 micro inches, most preferably with an arithmetic roughness value between about 10 and 50 micro inches.